Evaluation of shielding efficiency of using boric acid as coolant in CFETR vacuum vessel

Abstract

Vacuum vessel is a hermetically sealed steel container made up of double steel walls and in-wall shielding, which shields the neutron and protects other components in fusion reactor. Cooling water circulates through the vessel's double steel walls and removes the heat generated during operation. Since boron-10 has a large neutron absorption cross-section, boric acid is supposed to have better shield effect than the original cooling water. In this paper, the effectiveness of pure water and boric acid watery solution as coolant between the double steel walls of the vacuum vessel of CFETR is evaluated by Monte Carlo method. In the simulation, shield efficiency of pure water and different concentration of boric acid is investigated. Neutronic characteristics including neutron flux and neutron spectrum have been calculated. The result shows that boric acid can significantly reduce the flux of total neutron, while the flux of fast neutron takes less change. In conclusion, boric acid has better neutron shielding efficiency than water and can make total neutron flux decline 35%.